My long-term goals involve elucidating intracellular mechanisms that mediate hormonal regulation of steroidogenesis in each of two functionally distinct types of steroidogenic luteal cells (small and large). In the near future, I hope to investigate factors that regulate steroidogenesis in the large cell with specific focus on the roles of enzyme abundance and intracellular calcium. For these studies, I plan to collaborate (two individuals at this institution) in learning two new techniques for my lab (FURA-2 spectrophotometric fluorescence; Northern blot analysis). This will enhance the technical capabilities of my lab as well as generate new avenues of direct collaboration. Effect of RCDA: If an RCDA is awarded to me, it will greatly enhance my career development by 1) significantly reducing my teaching and service responsibilities 2) allowing me to hire a postdoctoral fellow for increasing the intellectual environment and research productivity in my lab. This will permit me to further develop collaborative contacts here and at other institutions. Institutional plans/environment: Previously, reproductive endocrinology has not been a highly visible area of research at the U. of Az. However, recently a number of new faculty positions in reproductive biology have been approved in this and other departments. Research facilities at the U. of Az. are excellent, and a highly cooperative atmosphere for interactive collaboration exists. Therefore, within the next decade, reproductive biology should emerge at the U of Az as a major area of representation. Proposed research: The ovine CL contains two functionally distinct types of steroidogenic cells, designated small and large. Whereas stimulated progesterone production in large cells appears to be uncoupled from hormonal regulation, the signal for luteal regression as induced by prostaglandin F2a (PGF2a) is probably mediated in these cells via calcium-dependent regulatory pathways. The proposed studies will investigate whether secretion of progesterone in large cells is regulated by cellular content of mRNA for side chain cleavage enzyme complex (the rate limiting enzymatic step in steroidogenesis in other tissues) and whether luteolysis in these cells is mediated by PGF2a working via direct changes in intracellular calcium levels. The specific aims of this proposal will utilize ovine small and large cells to 1) correlate secretion of progesterone and oxytocin with direct measurements of intracellular calcium as affected by PGF2a 2) compare the abundance of mRNA for side chain cleavage enzyme complex and 3) evaluate the effect of luteolysis on content of mRNA for side chain cleaveage enzyme. The results of these studies will provide valuable insight as to the role of the large cell in regulating luteal function.